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Abstract

This study aims to quantify and analyse emissions from marine vessels that can operate on liquefied natural gas (LNG) but continue to use conventional fuels, largely due to the limited availability of LNG bunkering stations (BSs) over long distances. Four regions have been identified as having high concentrations of LNG-fueled vessels but limited access to operational BSs: the West Coast of the United States of America (USA), South Africa–Good Hope–Madagascar, Northwest Africa, and Brazil. This selection is based on the geographical distribution of these ships and the existing infrastructure. Hourly greenhouse gas (GHG) emissions have been calculated by considering the power outputs of the main and auxiliary engines, specific fuel consumption (SFC) rates, and the emission factors for the vessels' liquid and gas operating modes. Container ships exhibit the highest hourly GHG emissions among vessel types, reaching 31.49 t/h in liquid mode and 23.68 t/h in gas mode. This is followed by crude oil tankers (6.3–14.01 t/h in liquid mode), bulk carriers (8.06 t/h in liquid and 6.06 t/h in gas), and car carriers (6.3–7.66 t/h in liquid mode). Gas mode provides a 19–29% reduction in emissions across these vessel categories. In hightraffic regions such as the West Coast of the USA and South Africa–Good Hope–Madagascar, annual GHG emissions from LNG-fueled ships total 1.84 Mt and 2.19 Mt in liquid mode, respectively. If gas mode is fully adopted, potential 24–26% reductions could significantly contribute to mitigating global maritime GHG emissions.

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